The invention relates to a jet-propulsive watercraft such as a personal watercraft (also referred to as a xe2x80x9cPWCxe2x80x9d) which ejects water rearward and planes on a water surface as the resulting reaction and, more particularly to a watercraft having auxiliary steering components as well as a main steering member such as a steering nozzle of a water jet pump.
Recently, jet-propulsive type watercrafts have been widely used in leisure, sport, and rescue activities. Such type of the watercraft is configured to have a propulsion pump, which is also called a water jet pump, to suck water (including seawater) through a water intake generally provided on a bottom of a hull. The water jet pump pressurizes the sucked water and ejects it rearward from the jet pump, thereby propelling the watercraft. While so propelled, the watercraft is turned to right or left by turning a steering nozzle, which is located rear side of the jet nozzle of the propulsion pump, rightward or left ward to change the ejecting direction of the water.
In the jet-propulsive watercraft, the propulsive force for turning the watercraft is reduced when amount of the water ejecting from the water jet pump is reduced to where the throttle of an engine mounted in the watercraft is closed. Therefore, the steering capability of the watercraft is reduced until the throttle is re-opened.
As for a reference, a Japanese Utility Model No. S63-180495 (1988) discloses a catamaran or twin-hulled ship which is provided with movable flaps on starboard (right) and port (left) sides of lower position of a transom board. At least one of the two flaps is lowered into water to generate a lift while turning the ship, thereby forcing the ship to bank inwardly. Because a ship which has the above type of hull shape has relatively large stability, the disclosed particularly describes a technology in which the centrifugal force acting on the turning ship is cancelled out by forcing the inward bank. That is, the ship is configured to lower one of the flaps, or to lower one of the flaps relative to the other on the opposite side of the turning. Therefore, the ship is to operate in completely opposite manner to the present invention as described hereinafter.
The present invention has been made with the aim of solving the above problems, and it is an object of the present invention to provide a watercraft which can maintain steering capability even while amount of water ejected from a propulsion pump is decreased.
A first aspect of the present invention is characterized by a watercraft, comprising: a hull; a steering mechanism for directing the watercraft by means of moving a steering nozzle of a propulsion pump in accordance with steering operation; and a pair of steering components, each of which is disposed on the right and left side of the hull at the level of water or below the water level, which are arranged so as to change resistance of water acting on the hull, wherein at least one of said steering components is operated to be in a xe2x80x9cFirst State (Operating State)xe2x80x9d in which the resistance of water acting on the hull is increased and to be in a xe2x80x9cSecond State (Non-operating State)xe2x80x9d in which the resistance of water acting on the hull is smaller than that of the First State.
Here, the position xe2x80x9cat or below water levelxe2x80x9d means such a position at which a portion of the steering component(s) is at or below the water level while it is in operation. Thus, it is not necessary that a whole part of the steering component be at or below the water level.
In such a structure of the watercraft, by operating one of the steering components from the xe2x80x9cSecond State (Non-operating State)xe2x80x9d into the xe2x80x9cFirst State (Operating State),xe2x80x9d the one of the steering components can increase the resistance of water acting on the hull of the watercraft. Therefore, either one of the right- and left-side of the steering components is operated to increase the resistance of water on the operated side so that the watercraft can be maintained in turning to a desired direction, even when the amount of water ejected from the propulsion pump is decreased.
The steering components may be used to reduce speed of the watercraft by operating both steering components from the xe2x80x9cSecond Statexe2x80x9d into the xe2x80x9cFirst State.xe2x80x9d
The steering component may be comprised of a plate-like member so as to protrude from the hull surface in such a manner that it is rotated about a supporting shaft.
Further, the steering component may be comprised of a member which is able to be recessed with respect to the hull bottom surface in the xe2x80x9cFirst State.xe2x80x9d In this configuration, the steering components can be with less resistance of water while being in the xe2x80x9cSecond State.xe2x80x9d
Preferably, the steering component may be recessed by means of a change in pressure generated by a fluid pressure generator contained inside the watercraft.
Still further, the steering component may be comprised of a member which can be protruded substantially vertical and downward from the hull bottom surface.
Preferably, the protruding steering component is comprised of a plate-like member which is arranged such that the plate surface is along the protruding direction thereof, and which is obliquely arranged with an angle with respect to water flow direction such that it directs the watercraft toward the side at which the member is protruded. In this configuration, addition to the effect of the generation of increased resistance of water acting on the hull by the steering component in the xe2x80x9cFirst State,xe2x80x9d the steering component has an effect such as it works in a rudder-like manner, thereby helping to turn the watercraft.
The steering component may be comprised of a plate-like member which is arranged on the bottom of the watercraft so as to protrude rearward from a transom board which is rear of the hull, and so as to be changeable in the mounting angle to the bottom surface of the hull. In this configuration, the steering components can be easily assembled and maintained. Moreover, both of the steering components may be operated simultaneously so that transition from non-planing state to planing state can be smoothly carried out.
It is preferable that the watercraft is a personal watercraft wherein one of the steering components can be transformed from the xe2x80x9cNon-operating Statexe2x80x9d into the xe2x80x9cOperating Statexe2x80x9d in accordance with rightward or leftward operation of the steering handle disposed forward of a rider""s seat of the watercraft. Therefore, the steering components make an appropriate auxiliary steering mechanism for a personal watercraft in which low weight and simplicity is usually required.
Still further, the steering component is comprised of a plate-like member which is arranged on the bottom of the hull so as to protrude rearward from a transom board which is rear end of the hull, and so as to be protrudable downwardly from the bottom surface of the hull, while a cam is rotatably provided on the transom board so as to come in contact with the rearward protruded portion of the steering component from above. The cam coordinates with the steering nozzle of the propulsion pump and pushes down the steering component to transform it from the xe2x80x9cSecond Statexe2x80x9d into the xe2x80x9cFirst State.xe2x80x9d Therefore, the steering components can be easily assembled and maintained.
Preferably, the steering component is restored into the xe2x80x9cSecond Statexe2x80x9d by a spring while the steering component is not pushed down by the cam. Therefore, less resistance of water acts on the steering component in the xe2x80x9cSecond Statexe2x80x9d while cruising.
It is preferable that an external force absorbing mechanism is provided in a system for operating the steering components. When an external force is applied on the steering component such that it makes the steering component in the xe2x80x9cFirst Statexe2x80x9d transform to the xe2x80x9cSecond State,xe2x80x9d the external force absorbing mechanism absorbs the external force to transform the steering component from the xe2x80x9cFirst Statexe2x80x9d into the xe2x80x9cSecond State.xe2x80x9d
Preferably, the external force absorbing mechanism includes the cam for operating the steering components by coming in contact with and pushing the steering components to transform them from the xe2x80x9cSecond Statexe2x80x9d into the xe2x80x9cFirst State.xe2x80x9d The cam is comprised of two members which are coaxially and rotatably connected on a supporting shaft thereof, each member has an engaging surface being a side face of the member. The engaging surfaces of the two members are provided with mating teeth being mated together. The two members are biased by a spring such that the engaging surfaces of the two members are pressed onto one another. In this configuration, the external force absorbing mechanism is placed outside the watercraft exposed, thereby the external force absorbing mechanism can be easily assembled/disassembled and easily checked by eyes.
The external force absorbing mechanism may be connected with an elastic member in a system for operating the steering component from the xe2x80x9cSecond Statexe2x80x9d into the xe2x80x9cFirst State,xe2x80x9d the elastic member is elastically deformed for transforming the steering component from the xe2x80x9cFirst Statexe2x80x9d into the xe2x80x9cSecond Statexe2x80x9d when the external force acts on the steering component in the xe2x80x9cFirst State.xe2x80x9d In this configuration, the external force absorbing mechanism is simply constituted.
Still further, the external force absorbing mechanism is comprised of a first member and a second member. The first member is coaxially disposed on a steering column of the steering handle and is provided with a plane cam surface on one end thereof. The second member is provided with a plane cam surface so as to be in contact with the plane cam surface of the first member. The first and second members are pressed onto one another by a spring so that the cam surfaces are brought in contact. The second member is connected to the steering components by a connecting member(s). In this configuration, only one external force absorbing mechanism is needed to absorb the external force acting on the steering components.
A second aspect of the invention, is characterized by a watercraft comprising: a hull; a steering mechanism for directing the watercraft by means of operating a steering nozzle with which a propulsion pump is equipped; and a pair of stabilizers, which coordinate with the steering mechanism, each of which is movably provided on both right and left sides of the hull so that resistance of water acting on one of the stabilizers is changeable with respect to that of the other.
In this configuration, by steering operation of the watercraft, the stabilizer located on a turning side is made to be in a xe2x80x9cFirst Statexe2x80x9d in which the resistance of water acting on the stabilizer is increased relative to the other; or a stabilizer located on the opposite side is made to be in a xe2x80x9cSecond Statexe2x80x9d in which the resistance of water acting on the stabilizer is decreased relative to the other. The stabilizers can increase the resistance of water acting on one side relatively to the other of the watercraft, thereby turning the watercraft to any desired direction.
The stabilizers may be located at a height in which at least a portion of the stabilizer on the desired side of turning the watercraft comes in contact with water while steering operation. In this configuration, the resistance of water acting on the stabilizer in operation can be increased.
Still further, the stabilizers may be located at a height such that at least a portion thereof is in contact with water while steering operation is not carried out as well as while steering operation is carried out. Such a configuration has the same basic effects as mentioned above.
Preferably, the stabilizer comprises a stationary part and a movable part. Only the movable part is operated with respect to the stationary part in accordance with steering operation to change resistance of water acting thereon. In this configuration, the portion of the stabilizer which is movable is less in mass; therefore, the configuration is more preferred.
Preferably, the movable part is constituted such that resistance of water acting thereon is increased in accordance with steering operation. Therefore, the configuration is more preferred.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.